I purchased my truck a little over a year ago and the brakes are the one thing that I haven't really had trouble with even though it sat for 5-6 years. I just had to replace the two front hoses to pass inspection. They have great stopping power and everything. 4-5 months ago I started the truck cold and pulled out onto my gravel driveway and the brakes were really touchy. I never had noticed it like that before. Just going for a short drive and they seemed fine before I knew it. After that it happened off and on. For the past couple of weeks it seems like they have been touchy a lot more often and don't clear up 100% even after going down the road now. The pedal has never went "hard"

My guess is that it has something to do with vacuum. Does a lack of vacuum brakes to become sensitive? I know I pull a pretty small amount of vacuum, only about 9" of vacuum in drive, which explains why they did clear up after going for a little drive (vacuum reserves build up?) but even with the low vacuum the brakes seemed perfectly normal with the same engine configuration early this year and last year...

Have any of you guys have any thoughts or experience with this? You think the booster is going bad or it's just something simple like the check valve or something else completely?

 

Usually when they are touchy it's the rear wheel cylinders starting to fail.

 

I don't think it's power brake booster at all; without any vacuum, your power brakes become non-power-assisted and the pedal gets pretty dang hard to push.

Try this yourself with the engine not running; step on the brakes a few times to clear out the residual vacuum and notice that the pedal becomes lots harder.

You haven't specified if it's the front or rear brakes that are causing you the problem? Do your rear brakes lock up when the brakes become sensitive?

 

How can I check them?

I'll try that and report back. I believe it is the rear brakes, but I rarely hear any of the tires skid, it's just enough so that it really annoys me.

 

Well when they stick they'll slow the truck down in a hurry. On my truck they would actually lock up the rear wheel. With the original tires of course. You can pull off the drum and look for leaking from the wheel cylinders.

 

We Had a 87 f150 that the brakes felt like you slamed on the brake when you barely touched it. ours ended up being a bad brake booster. we figured it out after replacing most of the systems. mainly because my uncle had replaced the brake booster about a year ago.

 

My Bronco is exactly like what you describe. It's in the rear, and it's worse on damp mornings if it rained the night before.

I plan to rebuild the rears this month (I hope). I'll check in and let you know what I find when I do.

 

Maybe that's why they've been more sensitive lately. It has been raining a bunch. And when it's not raining it's extremely foggy and humid.

 

No... I really doubt the water is causing this; if it were the cause, it would be more common knowledge that wet brakes behave this way, and the insurance industry would be hit with a rash of claims every Springtime as people run into each other every time it rains.

In fact, it's common knowledge that water reduces the effectiveness of brakes, not increases it.

The rear brakes on my F350 are behaving similarly right now, but I know it was caused by me because the symptoms began directly after I had removed & reinstalled the drums.

I probably (at least, I hope I) don't have the shoes oriented in the correct position and/or adjusted incorrectly, but it could also be caused by leaking wheel cylinders, broken lining material, grease contamination, etc. etc. etc.

Here are some pictures of some broken lining material, this happened after the brakes overheated for an extended amount of time:

 

Hey Chris,

I know what you're saying, but it's absolutely consistent and predictable for me. If it rained during the night, my rear brakes are touchy to the point of being dangerous in the morning. Just as soon as I warm 'em up a bit (4 or 5 stops in the neighborhood), they act fine. Dry nights and they are just fine in the mornings.

I've been told that ceramic pads will alleviate this symptom. Don't know how true that is, but the guys over at the Bronco forum swear by that.

 

Yo, Kev,

I'm not trying to say you're hallucinating or anything, but would it make sense to you that there is at least one other issue with your brakes (contamination, misalignment, whatever) that is being amplified or accentuated by the presence of water and thereby appearing to cause your symptoms?

Because, if you think about it, industry has been producing these brakes for something close to 100 years, but I doubt society would find them acceptable if a side-effect of getting wet was to have your wheels lock up.

Management would go to Engineering and tell them to fix that because the lawyers have lost too many lawsuits.

 

Yea, for all I know it's caused by a light film of surface rust on the inside of the drum, acting as an additional friction agent causing the pads to grab better. That's why it only does this after sitting up overnight. Wear the rust off with a couple of stops, and all is well.

It's not the water itself.... As I said, let me tear into them here shortly and I'll report what I find.

 

Not sure what the cause is, but on my 95 B2300 (ranger) the front brakes are quite touchy the first couple uses after sitting thru a rain, or an extremely humid night (foggy).
I know it goes against all logic, moisture on brakes *should* reduce their effectiveness.

A light application of the pedal while driving thru the nieghborhood, all is good by the time I reach the first stop, 1 block down the road.

 

Chris, one of the problems I have been seeing is ever since asbestos was banned, there seem to be two types af brake material. Vegtable or semi-mettalic, the first one tends to be grabby and short lived, the second lasts, but doesn't stop quite as well as asbestos and is harder on the drums and rotors.

If you want interesting brakes, my 66 GT-350 had very hard pads on the front brakes and full mettalic (Lakewood Velvetouch) on the rear with no power booster (no early Mustangs had power brakes and manual trans). In the winter, you had better drive a couple of blocks with the parking brake partially applied or it had no brakes.

 

My 96' is the same way. No leaking cylinders, and its done this with 3 different sets of shoes and 2 different sets of drums. I first noticed it the year I bought the truck, 2004. And it still does it to this day. If its been a moist night, I just step on the pedal hard in the morning before I leave the parking lot/driveway. If I just drive off and step on the brakes and I'm on any sort of loose sand or gravel the rear wheels just drag till the fronts start braking and I stop. Not sure what the deal is, fronts never grab hard regardless of the air's moisture content, its only the rears.
Either way, seems like so long as you're aware of it, its not a big deal.